Seems like what you're looking for is an enclosed equipment cabinet, not a rack per se. Tubes are probelmatic when it comes to vibrations. They are particularly susceptible to airborne vibrations and microphonics. An enclosed cabinet would help with airborne vibrations but keep the need for cooling in mind too. Depending on your taste, that could make your budget tough to hold to. What is your decor?
my 2 cents:
1. Isolate yourself from the world as best you can, this will allow you to hear more at lower sound pressure levels (spls). Lower spls mean less airborne and self induced vibrations.
2. If you listen loud (BTW extended exposure to 85 dB or more will result in permanent hearing loss or possibly worse) consider enclosing your equipment or moving as many components as possible to another room.
3. For soft (wooden) floors use soft supports (pillows, air bladders) or consider using brackets that are secured to the walls (if the walls are stiff).
4. Use heavy/coupled supports on concrete slab floors.
5. Devices that behave differently vertically than horizontally (like flexi-racks or roller balls) make no sense and removing covers is counterproductive in terms of vibration control.
Personally I keep the spls down and use a small $30 Ikea "Corras" nightstand for my simple system. My well isolated dedicated listening room has a concrete slab, so I left the rollers off the bottom of my "rack" so that the posts that the rollers attach to are allowed to act to some degree like spikes. I then use a 2nd matching nightstand as a side table at my listening chair that allows me to add a 4th shelf if needed in the future. In total a $90 and one hour investment. The "rack" elevates the controls for my convenience, permits short cable runs, and stays unobtrusive for imaging/soundstaging.
See my recent related post elsewhere.
